You had an invalid email address.
I close accounts with invalid email addresses since I can't contact the person to tell them it's invalid
Thanks for the response -
I can confirm 2 things - (1) the e-mail address is indeed valid and (2) the e-mail service for the domain is presently down - but will be back up in 3 hours.
dsn=4.0.0, stat=Deferred: xxx: No route to host
I call that an invalid email address.
Yes it's a static IP, yes it pings, but no there's no email server there.